Closely allied to S. graminoides, but stems unbranched and sometimes twisted, 20-40cm tall. Spathes two, one much larger. Flowers 2-2.5cm across, rich purple-blue with a yellow eye, summer. Plants less than 20cm in height and with somewhat larger flowers are sometimes known as S. macounii and S. sarmentosum, syn. S. birameum. In cultivation these dwarfs may be confused with S. helium, a normally taller, branched species, q.v. Some botanical authorities consider S. idahoense to be part of the variability of S. graminoides. If this becomes generally recognised and S. sarmentosum is also included, then sarmentosum being the oldest name, would have priority for the whole complex. S.i. 'Macounii Album' is a dwarf form with pure white flowers.